There are a variety of exercise devices of various volumes having to do with the structural complexity and the purpose of the exercise devices. In other words, a device designed for exercising all parts of a human body is bound to have a rather bulky volume. It is therefore conceivable that such bulky exercise device takes up a large area of the floor space, not to mention the high cost of making or shipping the exercise device. In general, the exercise devices consist of a base which is provided with the action elements, depending on the purpose and the function of the base. The base is mainly composed of a plurality of rodlike members. The volume of an exercise device is therefore dependent on the volume of the base. According to the conventional practice, the rodlike members of the base are connected by welding. However, the current practice involves the application of pivoting elements enabling the rodlike members to swivel in relation to one another. The rodlike members are provided with a plurality of locating holes and threaded holes engageable with pins or bolts for fastening pivotally the rodlike members such that the base can be folded or unfolded. However, such a foldable base as described above is difficult to use.